Since the early years of the United States there has been a gradual westward shift in the mean center of population. In 1790 the most populated cities in the U.S. were all on the East Coast. In the 2010 census seven of the ten largest cities were located in the Sun Belt region of the south and west. …A few weeks ago I saw a really interesting animated GIF, posted to Reddit, which mapped the top ten cities by population by decade in the United States. …Being an animated GIF means that you can’t interact with the map. I really wanted to play with the map so I decided to create my own interactive map of the same data.